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Title: Photochemical Oxidation of Dissolved Elemental Mercury by Carbonate Radicals in Water

Photochemical oxidation of dissolved elemental mercury [Hg(0)] affects mercury chemical speciation and its transfer at the water-air interface in the aquatic environment. The mechanisms and factors that control Hg(0) photooxidation, however, are not completely understood, especially in natural freshwaters containing dissolved organic matter (DOM) and carbonate. Here, we evaluate Hg(0) photooxidation rates affected by various reactive ionic species [e.g., DOM, CO 3 2-, NO 3 -] and free radicals in a creek water and a phosphate buffer solution (pH=8) under simulated solar irradiation. We report a high Hg(0) photooxidation rate (k = 1.44 h -1) in the presence of both HCO 3 2- and NO 3 -, whereas HCO 3 2-, NO 3 -, or DOM alone increased the oxidation rate slightly (k = 0.1 0.17 h -1). Using scavengers and enhancers for singlet oxygen ( 1O 2) and hydroxyl (HO ) radicals, as well as electron paramagnetic resonance spectroscopy, we identify that carbonate radicals (CO 3 ∙-) primarily drive the Hg(0) photooxidation, whereas addition of DOM resulted in a 2-fold decrease in Hg(0) oxidation. This study identifies an unrecognized pathway of Hg(0) photooxidation by CO 3 ∙- radicals and the inhibitory effect of DOM, which couldmore » be important in assessing Hg transformation and fate in water containing carbonate such as hard water and seawater.« less
 [1] ;  [2] ;  [3] ;  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhejiang Univ. of Technology, Hangzhou (China)
  2. Zhejiang Univ. of Technology, Hangzhou (China)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; SC0007042
Accepted Manuscript
Journal Name:
Environmental Science & Technology Letters
Additional Journal Information:
Journal Volume: 1; Journal Issue: 12; Journal ID: ISSN 2328-8930
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; mercury; photo-oxidation; reduction; carbonate radical; 54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1239560